1. Field of the Invention
The present invention relates to a method and system for preventing mixing of materials, in which, in the course of the production of a crash pad through the simultaneous injection of two different types of resins, the penetration of one type of resin into the region of the crash pad, which is filled with another type of resin, is effectively prevented.
2. Description of the Related Art
Generally, a crash pad is mounted onto the front of the interior of an automobile, where a steering wheel and an instrument panel are located.
Such a crash pad is conventionally manufactured by subjecting one type of synthetic resin to injection molding using a mold. Further, because an airbag is provided these days to the passenger seat of an automobile, a PAB (Passenger-side Airbag) door for use in the inflation of the airbag is defined by a laser-processed tear line at the portion of the crash pad where the passenger-side airbag is mounted. Recently, through two-shot molding, that is, the simultaneous injection of two different types of resins, the portion of the crash pad to which the passenger-side airbag is mounted, including the PAB tear line, is formed using a highly soil material, thereby producing a crash pad which allows the PAB door to be more easily opened.
Generally, examples of the first material for the entire crash pad include PPF (PolyPropylene fiber) resin, having high hardness, and examples of the second material, which is charged in the PAB door region, include TPO (ThermoPlastic Olefin) resin or TPE (ThermoPlastic Elastomer) resin, having high softness.
However, when two different materials are used to produce a crash pad, the different materials mix at the boundary thereof, undesirably making the strength of the tear line of the PAB door region non-uniform, resulting in irregular breakage of a PAB door upon the expansion of an airbag, which is regarded as a serious defect that compromises the safety of a passenger.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.